For these sufficient reasons it is Utopian to look forward to the day when the occult shall have disappeared, and the lion and the lamb shall feed and grow strong on the same nourishment. Doubtless new forms and phases of the occult will arise to take the place of the old as their popularity declines; and the world will be the more interesting and more characteristically a human dwelling-place for containing all sorts and conditions of minds. None the less it is the plain duty and privilege of each generation to utilize every opportunity to dispel error and superstition, and to oppose the dissemination of irrational beliefs. It is particularly the obligation of the torch-bearers of science to illuminate the path of progress and to transmit the light to their successors with undiminished power and brilliancy; this flame must burn both as a beacon-light to guide the wayfarer along the highways of advance and as a warning against the will-of-the-wisps that shine seductively in the bye-ways. The safest and most efficient antidote to the spread of the pernicious tendencies inherent in the occult lies in the cultivation of a wholesome and whole-souled interest in the genuine and profitable problems of nature and of life, and in the cultivation with it of a steadfast adherence to common sense and to a true logical perspective of the significance and value of things. These qualities, fortunately for our forefathers, are not the prerogative of the modern; and, fortunately for posterity, are likely to remain characteristic of the scientific and antagonistic to the occult.
BIRDS AS FLYING MACHINES.
By FREDERICK A. LUCAS.
From the day of Solomon onward the way of a bird in the air has been a subject of general interest, and the attention given to the problem of aerial navigation of late years has caused the flight of birds to be carefully studied in the hope that it might throw some light on the subject. There have been many conceptions, not to say misconceptions, regarding the flight of birds; it has been assumed that their muscles exerted a power quite beyond that of other animals, that the air sacs of some birds and the hollow bones of others gave them a degree of lightness quite unattainable by the use of ordinary materials, while some have even gone so far as to suggest the presence of some mysterious power, something like Stockton’s negative gravity, whereby birds could set at naught the law of gravitation and rise at will like a balloon. The strength of a bird’s muscles, of some birds’ muscles at least, is not to be underrated; a hawk will plant its talons in a bird of nearly its own size and weight and bear the victim bodily away, and an osprey will carry a fish for a long distance. But a tiger has been known to fell a bullock with a single blow of the paw, to carry a man as a cat would carry a rat and to drag an Indian buffalo heavier than himself. On the other hand, some of the petrels, birds which can pass a day or so on the wing with ease, cannot rise from the water after a hearty meal, and the humming-bird, unsurpassed in aerial evolutions, may be trapped in a spider’s web. This shows no great power, and long ago Marey found that the pulling force of a hawk’s great breast muscle, applied through the humerus, amounted to 1,298 grams per square centimeter, something like seven pounds to the square inch; not a very heavy pull. So it seems fair to assume that while the power exerted by a bird is great, it is very far from marvelous, probably far less in proportion to size than the engine of Maxim’s great aeroplane, or the naphtha motor of Professor Langley, which weighs less than ten pounds per horse power. We may get a fair idea of what this means by remembering that a bald eagle weighs from nine to fifteen pounds and that he exerts but a small fraction of a horse power.
Turning to the question of the part played by the air sacs it may be said that their value is not proved; some of the fastest birds get along without them, while birds of the most labored flight are sometimes well provided. In birds like the gannet and brown pelican the air sacs and cellular tissue about the body undoubtedly serve as buffers to break the shock of a headlong plunge into the water from a height of a hundred to a hundred and fifty feet. Or, again, they equalize the internal and external pressure when a soaring bird drops suddenly from a great height, or still more often aid in oxygenating the blood.
The hollow bones of birds are frequently cited as beautiful instances of providential mechanics in building the strongest and largest possible limb with the least expenditure of material, and this is largely true. And yet birds like ducks, which cleave the air with the speed of an express train, have the long bones filled with marrow or saturated with fat, while the lumbering hornbill that fairly hurtles over the tree tops has one of the most completely pneumatic skeletons imaginable, permeated with air to the very toe tips; and the ungainly pelican is nearly as well off. Still it is but fair to say that the frigate bird and turkey buzzards, creatures which are most at ease when on the wing, have extremely light and hollow bones, but comparing one bird with another the paramount importance of a pneumatic skeleton to a bird is not as evident as that of a pneumatic tire to a bicycle.
While it may not be easy to disprove Herr Gätke’s assertion that birds sustain themselves in the air by the exercise of some power beyond our own, it is pretty safe to assume that they do not, and it would seem that the burden of proof should lie with those who take the affirmative side of the question.
If we have nothing to learn from birds in the way of building an engine that shall exert great power for its size and weight we may still have something to gain in the matter of speed, although here the popular idea is apt to be exaggerated. We often read that ducks fly at the rate of a mile a minute, or that the swallow has a speed of two hundred miles an hour, but it is very difficult to lay hands upon any facts that will sustain these assertions.
So, too, homing pigeons are frequently stated to have travelled for long distances at the rate of sixty miles an hour, but some of the published records show that one hundred and twenty miles in two hours and a quarter is unusually fast traveling, and this is at the rate of only nine-tenths of a mile per minute, a speed not unusual for express trains. However, it may be said that actual observations show that ducks do travel from forty to fifty miles an hour, and any sportsman will readily believe that under some conditions they attain a velocity of a mile and a quarter a minute, although a confession of faith is not a demonstration of an assured fact.